WASHINGTON
— As one of the most respected advocates practicing before the US Supreme Court, John Roberts held that a good lawyer should be able to argue either side of a case.

Now he's using a variation of that same strategy and all the skills he honed under intense High Court questioning to try to win Senate confirmation as the 17th chief justice of the United States.

His plan: reveal just enough information about his approach to judging to convince the senators of his integrity and constitutional expertise - but not enough to permit someone to forecast how he might vote once on the high court.

Roberts isn't just fighting for himself. If he is successful in holding that line he will help set the stage for the president's next high court nominee - the pick that will replace centrist Justice Sandra Day O'Connor and potentially swing the court to the right.

So far, Roberts has fended off, dodged, and sidestepped his way through a gauntlet of Senate Judiciary Committee questions involving the abortion precedent Roe v. Wade, efforts to strike down congressional enactments under the commerce clause, and the president's power to wage war independent of congressional guidance.

The bottom line: Senators - and the American public - are learning precious little about which way Roberts is likely rule as the nation's most powerful judge.

To Roberts, refusing to reveal how he might rule is important because in his view it upholds the special role of unelected, life-tenure judges in a representative democracy.

"It's based on the concern that the independence and integrity of the Supreme Court depend upon justices who will decide issues there with an open mind based on the judicial decisional process, not based on prior commitments they made during the nomination hearing," Roberts told the committee.

"All the justices have adhered to that approach," he says. "And if I'm to join their number, I need to be able to look them in the eye in the conference room and say I kept the same faith with the independence and integrity of this court."

That's the view of a judge and prospective chief justice.

But the issue looks a bit different from a seat in the US Senate, particularly on the Democratic side of the aisle, with constituents worried about threats to the abortion precedent and broad court rulings upholding civil rights.

While discussing constitutional precedents, Roberts frequently highlights both sides of the issue, leaving senators to guess which side of the argument he personally favors.

"He is doing a delicate dance trying to please everyone," says Nan Aron, president of the Alliance for Justice, which opposes the Roberts nomination. "At the end of the day people are going to walk out of this hearing room being uncomfortable."

Ms. Aron, a well-known watchdog of the judicial selection process, says Clinton high court nominees Justices Ruth Bader Ginsburg and Stephen Breyer were both more forthcoming than Roberts during their confirmation hearings. While many liberals are worried about Roberts's lack of candor, some conservatives seem pleased, even reassured by his cautious approach.

"We are not concerned," says Andrea Sheldon Lafferty, executive director of the Traditional Values Coalition. "We are looking for a jurist who will faithfully interpret the Constitution. We are not asking for someone who is pro-life."

Ms. Lafferty adds, "We believe he will be an honest jurist."

Roberts was repeatedly asked about his vigorous defense of White House power while serving as a lawyer in the Reagan administration. And more recently, he was a member of a three-judge appeals court panel that upheld the Bush administration's position on military tribunals for Al Qaeda suspects.

In reply, Roberts told the senator that one of the former Supreme Court justices he most admires is Robert Jackson. Justice Jackson was an advocate for White House power as President Franklin D. Roosevelt's attorney general before his nomination to the high court.

But in 1952, Justice Jackson voted to rein in presidential authority in invalidating President Truman's attempt to take over steel mills during the Korean conflict.

"Although he had strong views as attorney general, he recognized when he became a member of the Supreme Court that his job had changed," Roberts says.

The drawback of being such a gifted advocate is that it is sometimes difficult for observers to know when he is merely acting as an effective lawyer fighting to win a case and when he is speaking from the heart.

But there are moments during the hearing that point to the "real" John Roberts, and perhaps even the judge he is striving to become.

One of those moments came when he recalled one of his judicial mentors, Judge Henry Friendly who served on the federal appeals court in New York City.

"With Judge Friendly, it was just a total devotion to the rule of law and the confidence that if you just worked hard enough at it, you'd come up with the right answers," Roberts says.

"He liked the fact that the editorialists of the day couldn't decide whether he was a liberal or a conservative."

What the editorial writers failed to understand, Roberts says, is "he wasn't adhering to a political ideology, he was adhering to the rule of law."